First came word of a woman stabbed . Then screams . Then gunshots .

But the full story of Thursday 's gruesome beheading at an Oklahoma food processing plant -- especially why it happened -- is still waiting to be told .

One day later , there are tears for Colleen Hufford , the 54-year-old woman whose head was severed . There are prayers for 43-year-old Traci Johnson , who is in stable condition at a nearby hospital for treatment of `` numerous wounds , '' according to police .

And there are questions about 30-year-old Alton Alexander Nolen , the man who authorities say attacked them both and might have gone after more people if not for the company 's CEO , also an off-duty reserve sheriff 's deputy , who confronted and shot him twice .

Answers may come from Nolen himself . As of 6 p.m. -LRB- 7 p.m. ET -RRB- , he was `` coming out of a sedation '' at a hospital and investigators planned `` to attempt to begin interviewing him as soon as he was coherent enough to understand what was going on , '' according to Sgt. Jeremy Lewis of the Moore Police Department .

Here 's what they do know :

The attack happened very soon after Nolen learned he 'd lost his job .

Nolen had been incarcerated until March 2013 , for possession of a controlled substance , escaping confinement and resisting an officer .

And he had been trying to convert co-workers to Islam .

Lewis also said there may be other information about Nolen 's past , that he could not reveal , that might help explain the incident , and that the FBI had been called in to dig deeper into Nolen 's background .

`` Once we started investigating this initially , and started finding some of the things that he had been involved in , some of the things that he had been saying , we immediately contacted the FBI and got them involved , '' Lewis told CNN 's Erin Burnett .

CEO/reserve sheriff 's deputy stops attack

The large , rectangular Vaughan Foods processing plant looks like many others from the outside : a no-frills design , nondescript front entrance and loading bays out back .

But Friday , there was nothing normal about it . Police cars were everywhere , and uniformed officers walked the property . Some citizens stood outside watching , putting their arms around each other and trying to make sense of the horror the day before .

Some of this drama could be heard in a 911 call released Friday by the city of Moore .

It starts with a man yelling out , `` Shut the doors , '' before calmly turning his attention to a 911 dispatcher .

`` We have someone attacking someone in the building , '' he says .

The initial violence happened near the Vaughan Foods plant 's main entrance , but did n't stop there . According to a 911 call , the suspect went through the front office , to the shipping office , then over to a customer service office .

Did he know who he was attacking ? Not according to Lewis , who said the suspect used a knife -- which , otherwise , would be used in the processing of produce at the plant -- to randomly inflict bloodshed .

`` He was n't targeting anyone , was n't going specifically after them , '' the police spokesman said . `` It appears they were just in his way as he came in . ''

The onslaught 's end could be heard on the 911 call , when the caller 's steady voice was interrupted .

`` Can you hear this in the background ? '' he tells the dispatcher . `` And that , that 's a gunshot . ''

Three shots rang out in total , according to the caller .

There 's no indication that the suspect , Nolen , was armed with anything other than a knife . Of course , no one knew that at the time : They only knew that someone had entered their workplace , beheaded one woman , then attacked another .

Mark Vaughan -- who besides being his company 's CEO has been a reserve deputy with the Oklahoma County Sheriff 's Office since June 2010 -- `` did n't hesitate '' after learning that there was a killer on the loose , Sheriff John Whetsel said in a statement .

Instead , he confronted and twice shot Nolen , who is now hospitalized in stable condition .

`` Without regard to himself or his safety , '' Whetsel said , `` yesterday Mark Vaughan became a ` HERO ' while doing the job he was sworn to do -- protecting others . ''

Beheading raises questions , but officials say no terror link

The idea that a man who 's been trying to convert others to Islam ends up beheading someone is alarming enough , but perhaps even more given what has been happening in the Middle East .

The Islamist extremist group ISIS has made a name for its itself using such tactics , going so far as to record the beheadings of American journalists James Foley and Steven Sotloff as well as British aid worker David Haines .

And they 've threatened more to come , especially if the United States and its allies continue to launch airstrikes at the group in Iraq and Syria . This has spurred concerns that ISIS sympathizers may similarly lash out against innocents in the West .

That said , it 's not known if Nolen 's religion had anything , at all , to do with what happened Thursday .

The FBI and other investigators , of course , could eventually find some sort of link or tie Nolen to others .

But that has n't happened yet . As of Friday , all U.S. law enforcement officials said was that there are no indications linking the Moore attack to terrorism .

A spokesman for Oklahoma Gov. Mary Fallin , Alex Weintz , noted the governor had blocked Nolen from receiving parole in 2012 , but said she `` believes we need to let law enforcement do their job and not to jump to any conclusions before the conclusion of the investigation . ''

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Oklahoma governor warns against `` jumping to conclusions ''

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Suspect in beheading , Alton Alexander Nolen , was a recent convert to Islam

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Suspect is in a hospital and will be interviewed once he 's `` coherent enough , '' he adds

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The man allegedly beheaded a woman , attacked another ; an off-deputy deputy stopped him